“Koko touched the lives of millions as an ambassador for all gorillas and an icon for interspecies communication and empathy,” the release said. “She was beloved and will be deeply missed.”

The western lowland gorilla was born at the San Francisco Zoo in 1971 and began to learn sign language early in life. She was said to have understood some 2,000 words of spoken English.

Researchers moved her to Stanford in 1974 and established The Gorilla Foundation, a non-profit organization that works to preserve and protect gorillas. Koko and The Gorilla Foundation then moved to Santa Cruz Mountains.

The foundation says she has taught the world a profound amount about the emotional capacity and cognitive abilities of gorillas.

Koko appeared in several documentaries and twice on the cover of National Geographic. The first cover featured a photo she’d taken of herself in a mirror, the foundation said.

She was widely promoted through appearances and the release of a picture book about her and a kitten that lived with her.

She has also been exhibited as a painter.

The foundation will continue its work on conservation and preservation of gorillas with continued projects, including a sign language application featuring Koko.